1. Field of the Invention
The present invention relates to a fabrication method and a structure of a through silicon via (TSV).
2. Description of the Prior Art
In the field of semiconductor technology, a TSV structure is utilized for interconnect between die and die to provide electrical connection of the devices on each level, such that the linking distances of devices disposed on a chip can be remarkably reduced, and, in turn, the overall operation speed can be effectively increased. In another technology such as semiconductor packaging, there are many ways such as wire bonding or flip chip combining wire bonding technologies to stack IC chips vertically. In recent years, silicon interposer with TSV (through silicon via) interconnect technology has gained increasing attention. It provides relatively high routing density and very fine pitch with good electrical performance.
Ordinarily, the TSV structure is obtained by forming a via hole on the front side of a wafer by etching or laser process and filling the via hole with a conductive material, such as polysilicon, copper or tungsten, to form a conductive path (i.e. the interconnect structure). Finally, the back side of the wafer, or die, is thinned to expose the conductive path.
However, the via hole is formed on the front side of the wafer, and after the conductive material is filled into the via hole, a surplus of the conductive material located on the interlayer dielectric is often removed by performing a chemical-mechanical polishing (CMP) process. In such process, a loading effect takes place during the grinding procedure that an abrasion rate in a region having a dense pattern and an abrasion rate in a region having a sparse (non-dense) pattern are different. Suffering from the loading effect, two regions which are supposed to be electrically separated from each other by removing conductive material using the CMP process tend to be not successfully separated due to a metal bridge structure formed on top surface of the TSV after the planarization; and accordingly the yield or quality of the products are affected.
Therefore, there is still a need for a novel fabrication method of TSV structures to avoid the aforesaid problems.